What would it take to add "tag notification" to this plugin? I just read the description and it does everything I want, except for the ability of users to subscribe to posts with certain categories AND/OR tags. Let me know how much work it would take, and if it's bounty you want - how much?

Shouldn't be too much work. Maybe 2 or 3h. The Problem is, that I'll will finish my Diploma/Master Theses until monday and am really looking forward to my vacation! To get this to release Quality it'll be a bit more work. (Adding options for people to turn it on or off, etc). If you know php or know someone who knows php im willing to point you in the right direction.

I have been using your plugin for a few weeks and have to say that my readers and I love it. I have been asked the same question from a couple of my readers if i could add tags also. I know you can add labels through the gdata api. It would be great to add tags as labels for my subscribers. I know a little php so if you don't have the time i would be more than happy to tinker with the code if you could point me in the right direction.